On many wheel-borne trolleys, chairs (wheelchairs) and small-scale vehicles, there is a need in this Art to provide some form of brake device for achieving securer and safer driving or transport. However, prior Art brake devices have not proved to lend themselves to mounting, without considerable modifications, on trolleys, chairs (wheelchairs) and small-scale vehicles which havenot already been adapted for this purpose on their manufacture. Sweeping modifications of this type often prove to occasion such prohibitively high costs that it is not deemed feasible to provide the finished product with a brake device, a lower standard of security and safety being instead tolerated in the handling of the trolley, chair (wheelchair) or small-scale vehicle. Thus, there is an urgent need in this Art for a brake device which is simple and reliable in both its construction and function and which is capable of being mounted on different models of trolleys, chairs (wheelchairs) and small-scale vehicles without their requiring any modification whatsoever.